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bio website lightandmatter.com
location Fullerton, California
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I teach physics at Fullerton College, a community college in Southern California. I have an undergrad degree in math and physics from Berkeley and a PhD in physics from Yale. Back when I was doing research, my field was experimental low-energy nuclear physics.


Aug
18
comment Does or should the metric expansion of space imply a locally observable increase in kinetic energy?
The case of an atom is qualitatively different from the case of a solar system. The solar system does theoretically have a secular trend of growth due to cosmological expansion, but the amount is much too small to measure. An atom does not show any such secular trend, even in theory, because it is a quantum-mechanical system with a well-defined ground state. I gave some numerical estimates in this answer: physics.stackexchange.com/a/70056/4552
Aug
18
awarded  nuclear-physics
Aug
18
answered Would a three wheeled vehicle be faster than a four wheeled vehicle of the same weight?
Aug
18
comment Would a three wheeled vehicle be faster than a four wheeled vehicle of the same weight?
The top speed of the vehicle has nothing to do with how much energy you have locked up in the kinetic energy of the wheels. Most of this answer doesn't address the question or connect logically to the issue of 3 versus 4 wheels.
Aug
18
comment Would a three wheeled vehicle be faster than a four wheeled vehicle of the same weight?
What people usually learn in freshman physics is a model of friction due to Amonton and Coulomb. Let's call it the AC model. The AC model works for solid, rigid surfaces in contact. It fails for fluids and wetted or lubricated surfaces, and it doesn't describe rolling resistance such as what you get with a car or bike tire. At the axle you have a lubricated bearing. At the ground you have rolling resistance. Neither of these is described accurately by AC, so I would be suspicious of any answer that doesn't specifically invoke something beyond AC.
Aug
18
comment What determines the magnitude of force of an electromagnet?
What matters is not the size but the dipole moment. The dipole moment is proportional to the current, the number of turns of wire, and the area. If you treat it as a dipole-dipole interaction (which I think is only appropriate in the far-field limit), then what matters is the product of the two dipole moments, the inverse cube of the distance, and the orientations: en.wikipedia.org/wiki/… If they're not far from each other, then I suspect the problem is much more complicated, although there may be heuristics.
Aug
17
comment Trouble with the Lorentz law of force: Incompatibility with special relativity and momentum conservation?
A useful resource on this topic: web.mit.edu/redingtn/www/netadv/srLzMa.html
Aug
17
comment Wavefunctions and Quark Confinement
@HDE226868: I had thought a position-space wavefunction wasn't bounded inside a certain area. Yes, but that's also true for a hydrogen atom.
Aug
17
comment Wavefunctions and Quark Confinement
A quark's wavefunction extends throughout all of space (prior to any de-coherence)... Why would this be?
Aug
17
answered Magnetic force and relative frame
Aug
17
comment Is force a contravariant vector or a covariant vector (or either)?
possible duplicate of Forces as One-Forms and Magnetism
Aug
17
answered Lifetime of undiscovered element and its calculation
Aug
17
comment Which electromagnetic radiation is faster in water, microwaves or light?
Looks to me like microwaves are slower: physics.stackexchange.com/a/65817/4552
Aug
17
comment Which electromagnetic radiation is faster in water, microwaves or light?
It's not a generally valid rule that the index of refraction increases with frequency.
Aug
17
comment What's the biggest cube you could have before gravity rounded it?
@Thoth19: The Scheuer paper actually discusses mountains on neutron stars.
Aug
17
comment Which electromagnetic radiation is faster in water, microwaves or light?
I guess the index of refraction for microwaves would have a big imaginary component, since water absorbs microwaves so strongly.
Aug
17
comment What makes General Relativity conformal variant?
Hmm...so maybe it's an "or:" conformal invariance if $d=2$ or if there are no massive particles.
Aug
17
comment What makes General Relativity conformal variant?
related: physics.stackexchange.com/q/74998
Aug
17
comment What makes General Relativity conformal variant?
GR isn't conformally invariant. It only becomes invariant if there are no massive particles.
Aug
17
comment Accelerating masses lose energy?
It's not really acceleration $d^2x/dt^2$ that matters, it's $d^3x/dt^3$. A simple example is two sheets of mass falling toward one another; they give zero radiation. Another way of putting it is that you need an oscillating mass quadrupole. (You can't have a mass dipole.)